1. Field of the Invention
The present invention generally relates to an open-and-close hinge device suitable for use especially with a portable telephone. In automatic mode, simply push a button and a cam device will be rotated by a spring such that a cover attached to the base is automatically opened. However, if a user wants to open the cover manually, simply open the cover, and the corresponding cam will rotate through adjacent cam surface.
2. Description of the Prior Art
Conventionally, a portable telephone where a transmitter section and a receiver section, or a keyboard side and a display side, thereof are mounted separately on a fixed side body and a movable side body respectively to be folded in two and opened and closed relative to each other, is known, and for this purpose, such an open-and-close hinge device is known as shown, for example, in Japanese Patent Laid-open No. 8-125725, wherein a torsion spring wound spirally around a shaft is interposed resiliently between a mounting portion of the fixed side body and a mounting portion of the movable side body connected with each other via the shaft so as to be folded in two freely, and an arresting means for engaging one end portion of the torsion spring with the mounting portion of the movable side body only within a predetermined opening angle of the receiver section, is provided between the mounting portion of the fixed side body and the mounting portion of the movable side body while a cam mechanism is provided between the mounting portion of the fixed side body and the mounting portion of the movable side body, whereby the cam mechanism is operated by pushing a push-button disposed in an axial direction of the mounting portion of the fixed side body to rotate the receiver section to the position in which the arresting means arrests one end portion of the torsion spring, and wherein a locking means is provided for releasing the engagement of the movable side body with the mounting portion of the fixed side body by pushing the push-button against the mounting portion of the movable side body while a friction mechanism is provided for stopping the movable side body in a free stopping way when and after it reaches a predetermined opening angle, so that the movable side body is opened automatically to a predetermined angle relative to the fixed side body by pushing the push-button in a push style.
As the above-described conventionally known open-and-close hinge device of a push type requires many parts and the structure thereof is complicated, there have been disadvantages that it often has trouble and is expensive.